Shot cup

ABSTRACT

A shot cup  20  for a shotgun cartridge  10  is disclosed which is made of paper or other biodegradable fibrous material. The shot cup  20  serves to contain shot  26,  particularly non-lead shot which may be abrasive, during firing, and to prevent such shot contacting the gun barrel.

DESCRIPTION OF INVENTION

[0001] THIS INVENTION relates to shotgun ammunition, and, more particularly, to lead-free shotgun ammunition.

[0002] There is widespread ecological pressure and a consequential trend of legislation against the use of the traditional lead shot for wild fowling and other shotgun use, due to the toxic nature of lead. As a result, various alternatives have been proposed to lead as a shot material, with varying degrees of success. The most successful of these proposals to date has involved the use of metallic tungsten or other non-toxic heavy metal in the form of fine particles in a plastics binder, the resulting composite material being used to form shotgun pellets.

[0003] Unfortunately, most of the lead-free shot substitutes so far proposed are more prone to damage the bore of a shotgun than the traditional lead shot, although some such substitutes are more detrimental to shotgun barrels than others. Even the relatively benign tungsten-filled plastics material is slightly abrasive and may, over extended periods of use, tend to abrade the surface of a shotgun barrel, for example in the region of the “choke” where the bore narrows slightly towards the discharge end of the shotgun barrel.

[0004] In order to prevent such abrasion, it is normal to use, with such lead-free shot, a lightweight shot cup of plastics material comprising a generally cylindrical end wall which serves the same function as the conventional wad in conventional shotgun cartridges, but which has extending forwardly therefrom, (i.e. towards the discharge end of the shotgun barrel in use), a peripheral wall or skirt to define, with the base wall, a receptacle or chamber to hold the charge of lead-free shot. When the cartridge is fired in a shotgun, the cup, with the charge of shot therein, is propelled, by the exploding charge, from the gun barrel and is separated from the charge of shot by the retarding effect of the atmosphere upon the lightweight large-diameter shot cup, the retarding effect of the atmosphere on the shot cup being much greater than the retarding effect of the atmosphere upon the smaller, denser, individual shot pellets. Because, during the travel of the shot/shot cup package down the gun barrel during firing, the peripheral wall of the shot cup lies between the gun barrel and the charge of shot, the shot pellets themselves do not contact the gun barrel and thus do not abrade the latter and the shot cup itself, is not, of course, prone to damage the gun barrel. The shot cup also serves the additional function of preventing deformation of the shot pellets by high speed contact with the gun barrel. Such deformation is undesirable, because it tends to affect the shot aerodynamically, producing more “spread” than may be ideal. However, such plastics shot cups are themselves beginning to be perceived as a nuisance from the environmental point of view, since the discharged shot cup form a species of litter in the areas of the country where shooting is popular and, being plastics, tend to survive as such litter for many years.

[0005] It is an object of the present invention to provide an improved shot cup which is more environmentally friendly than such plastics shot cup.

[0006] According to one aspect of the invention there is provided a shot cup, as herein defined, for shotgun ammunition, comprising a base wall structure and a side wall structure upstanding from the periphery of the base wall structure, characterised in that the shot cup is made of paper or other biodegradable fibre composition.

[0007] According to another aspect of the invention there is provided a shotgun cartridge, comprising a cartridge casing, a propellant charge within the casing, a shot cup according to the first noted aspect of the invention within the casing in front of the propellant charge and a quantity of shot within the shot cup.

[0008] An embodiment of the invention is described below by way of example with reference to the accompanying drawing in which:

[0009]FIG. 1 is a schematic sectional view in longitudinal section through a shotgun cartridge incorporating a shot cup in accordance with the invention, and

[0010]FIGS. 2 and 3 are perspective views to an enlarged scale showing successive stages in the manufacture of the shot cup itself.

[0011] Referring to the drawings, a shotgun cartridge 10 comprises, in conventional manner, a casing comprising a generally cylindrical tubular body 12 of cardboard or plastics secured at a rear end thereof within a metal end cap 14 carrying a percussion cap 16. Within the casing, adjacent the cap 14 and percussion cap 16 is a propellant charge 18 of explosive powder and in front of the charge 18 is disposed shot cup 20 comprising a base wall 22 which fits closely within the cylindrical body 12, the shot cup having a generally cylindrical peripheral wall 24 closely adjacent the interior surface of the body 12. A charge of shot 26, which may, for example, be pellets of a composite material comprising particles of metallic tungsten in a plastics matrix, is disposed within the shot cup 20. A cardboard closure disc 28, fitting closely within the cartridge body 12 overlies the cup 20 and the shot charge 26 and is retained by crimping or upsetting the outer (forwardmost) peripheral edge of the cartridge body 12 inwardly slightly to overlie the periphery of the disc 28.

[0012] In accordance with the invention, the shot cup 20 is of paper and may, for example, be formed by winding several turns of a paper strip, coated with adhesive, around a cylindrical mandrel, to form a laminated open-ended paper tube as shown in FIG. 2 and, preferably before the adhesive has dried or set, upsetting an end region of the tube, of an axial length approximately equal to the radius r of the tube, inwardly, as illustrated schematically in FIG. 3, so that the end region, thereby forced into a number of overlapping folds, forms the base 22 of the cup. Any other convenient means for forming the paper cup may, of course, be used. The adhesive used in manufacture of the cup 20 is preferably a biodegradable or water soluble adhesive.

[0013] The paper or cardboard used for the shot cup is preferably of such a nature as to have a relatively low wet strength so that after use, the empty shot cups lying on the ground will rapidly break up upon exposure to rain. The paper may also be so treated as to enhance its susceptibility to fungi and bacteria in the natural environment, or at least is not treated with chemicals which would tend to reduce that susceptibility.

[0014] Whilst the cup 20 has been described above, by way of example, as a shot cup, for containing lead-free shot in the form of pellets of a composite material in a plastics matrix, prior to discharge of a cartridge incorporating the shot cup, it should be appreciated that the paper shot cup described, or a shot cup of other biodegradable material, may be used to contain shot of other types, such as shot of ferro-tungsten, bismuth, steel, or even the traditional lead. Furthermore, such a cup may also be used to contain pulverulent or particulate material other than shot, for example, material adapted to present a visually striking or alarming effect when fired from bird-scaring “guns”, or marking or irritant material for use by police forces, for example for crowd control or for temporarily disabling violent criminals without causing serious injury. 

1. A shot cup for shotgun ammunition, comprising a base wall structure and a side wall structure upstanding from the periphery of the base wall structure, characterised in that the shot cup is made of a biodegradable fibre composition.
 2. The shot cup of claim 1 , wherein the shot cup is made of paper.
 3. A shot cup according to claim 1 , wherein said biodegradable fibre composition is so made as to enhance its propensity for mechanical, biological or other breakdown when exposed to outdoors environmental conditions.
 4. A shotgun cartridge comprising a cartridge casing, a propellant charge within the casing, a shot cup in front of the propellant charge, and shot within the shot cup, the shot cup being made of a biodegradable fibre composition.
 5. The cartridge of claim 4 , wherein said shot cup is made of paper.
 6. A shotgun cartridge according to claim 4 , wherein said shot comprises pellets each comprising particles of dense material in a plastics matrix.
 7. A shotgun cartridge according to claim 6 , wherein said pellets each comprise particles of dense metal in a plastics matrix.
 8. A shotgun cartridge according to claim 7 wherein said pellets each comprise particles of tungsten in a plastics matrix. 